Equilibrium Distribution of Liquid during Sintering of Assemblies of WC/Co Cermets

Abstract

Assemblies were made by stacking on top of one another two cylinders of WC-Co cermets differing in mean WC particle size (relative size ratio of 3.5) and cobalt concentration (6 or 15 wt pct). These assemblies were bonded by heat treatment at 1400°C under protective atmosphere for a dwell time of 7 hours. After completion of the heat treatment, the distributions of the cobalt concentration and WC grain size as a function of distance from the original interface between the two cermets were analyzed by combining Vickers microhardness measurements and image analysis. At equilibrium, the Co content was always larger on the side containing the smaller WC particle size. The final partition of Co was compared with the predictions of a model developed for expressing the dependence of the solid/solid and solid/liquid interface areas on the system parameters: phase volume fractions, dihedral angle, particle size, and particle coordination. An excellent agreement is found when assuming an average WC coordination of 7.

Modeling the Capillary Pressure for the Migration of the Liquid Phase in Granular Solid–Liquid–Vapor Systems: Application to the Control of the Composition Profile in W-Cu FGM Materials

“…The opening angle b at the apex of the cone is straightforwardly related to n c . In a previous work, this model was applied to two-phase systems to derive the capillary pressure for liquid migration in binary solid-liquid mixtures [5] or the sintering stress in a solid-vapor system. [13] The above model makes use of eight parameters: the average particle coordination number n C ; the particle volume V P ; the density…”

“…[4] Migration or imbibition of liquid also takes place through sintering or desintering of the solid particle skeleton in dense solid-liquid materials with a gradient in the liquid composition or solid grain size. [5,6] The dynamics of migration is controlled by an equivalent pressure, which is commonly called the capillary pressure. For example, the capillary pressure P C for liquid infiltration in a circular tube of radius r is expressed as…”

Effects of Liquid-Phase Composition on Its Migration during Liquid-Phase Sintering of Cemented Carbide

“…[6] were plotted in Figure 11. The measured equilibrium liquid distribution for various bilayered samples in this study and in other reported studies [4,25] were included for comparison. The equilibrium liquid distribution should, in theory, follow the iso-P m contour lines.…”

Sintering Kinetics Across Pore Closure Transition Accounting for Continuous Increase in Grain Coordination with Density

“…The rheology of the system is supposed to be entirely governed by grain‐boundary diffusion. The model for the intermediate stage was already used in previous work for modeling capillary equilibrium in solid/liquid and solid/vapor systems with a percolating fluid phase . The model developed in reference for the final stage is a new model that considers closed pores centered at quadruple points at the periphery of grains with arbitrary value of coordination number.…”

“…The model for the intermediate stage was already used in previous work for modeling capillary equilibrium in solid/liquid and solid/vapor systems with a percolating fluid phase. [19][20][21][22][23] The model developed in reference 18 for the final stage is a new model that considers closed pores centered at quadruple points at the periphery of grains with arbitrary value of coordination number. The phenomena of pore growth by Oswald ripening and of separation of pores from grain boundaries are not considered.…”